Electrical Load
 

How much do you have set aside for your tank alone?.. I'm working on the electrical for my 265 and I'm down to one space left in my panel..meaning I can only dedicate one 20 amp circuit and one shared circuit. Will this be enough or do I need to consider a sub panel?

Full blown reef? You'll need a subpanel. You don't want everything on one or two circuits anyway...one blows and your tank is hooped until you notice. If you have dual returns, keep the pumps on separate circuits. Get multiple heaters, and put them on separate circuits. Etc. I'm a BIG fan of doubling everything up...cover the butt. Consider it reef insurance. :D

I'd probably give up my welder before I put a sub-panel in the house.. but yeah after I typed that I was looking at some tank builds to see what other people were doing.. Untamed has four dedicated circuits.

you can get duel breakers that are 2 breakers that fit into one slot, depending on your pannel manufacture, you can have up to 12 devices on a single breaker and you can load a single breaker to 80% of its load eg, 12A max on 15A breaker.
add up all the watts of your devices and divide by 120 and thats how many amps you will draw, so you need a breaker or breakers to fit that load.

Have 2 dedicated circuits and sharing on a third. Though none are maxed in either capacity or receptacles, advantage is they are independent and can turn off one part without effecting other for rewire or maintenance. Also since running GFI breakers (GFI receptacle on third) one can trip without crashing my whole system.